I have 2 great knives to recommend but one is M4. you need to enjoy the patina, it's nature doing it's thing which is okay in my book. The first is the Spyderco Gayle Bradley 2. It is a super solid workhorse of a knife.
In my opinion it is in the top 5 Spyderco's for EDC. Another knife that I really like is the Steel Will Mini Gekko, I have it in N690 and it keeps an edge for quite a. I know that it also comes in M390 and I think D2. The knife is basically a folding Light bushcraft hard use EDC. Keep in mind that it is made in Italy and as far as I am concerned the have special skill when designing and making things. The Gekko has the liners polished on both sides of each one and the backlock can be adjusted to accommodate complete flip-ability. And with a little more time it can also be a free dropper when closing. Watch your fingers, it will bite you if you give it a chance